The progression of tooth decay often necessitates excavation of pulp from the root canal of the unhealthy tooth. Such removal is conventionally accomplished by mechanically excavating and enlarging the size of the root canal with a reamer, then sterilizing and filling it with suitable bonding material. While pulp is removed, care must be taken to avoid encroaching on healthy tissues and excessive removal of tooth structure. In the detail oriented, high wear and nerve ridden canal environment, even a small amount of imprecision can translate into over penetration beyond the apical foramen, periodontal membrane. Such over penetration can cause contamination and damage to apical and other tissues, in addition to premature decomposition and patient discomfort. Conversely, an inadequate amount of penetration may cause infectious tissues to remain. Precise knowledge of the depth of the canal can help avoid such incidents.
The practice of locating the apex, or most bottom portion of a root canal, is conventionally accomplished via measurement of electronic signals that permeate the canal region. Conventionally, an endodontist inserts a first electrode into the root canal and contacts a second electrode to the gum or other tissues proximate the root of the tooth. One of the electrodes emits an electronic signal that is received by the second electrode. Variations on this general principle include simultaneous generation of multiple signals having different frequencies.
Electrophysiological studies show that the circuit between the measuring electrode and the oral electrode approximates an equivalent circuit comprised of a resistor and a capacitor connected in parallel. The magnitude of the detected resistance or impedance will vary as the tip of the inserted electrode approaches the apical position. As such, detected impedance, for instance, can be used to determine whether the leading edge of the measuring electrode has arrived at the apical position.
Prior art systems rely on algorithms to marry a ratio or other value derived from the measured impedance or resistance to an apical distance. For instance, many conventional processors use measured impedance to calculate electrode distance as a function of one or more preprogrammed equations. Processors typically execute an appropriate algorithm at periodic intervals to update calculated distances, which are reported to the endodontist.
Despite advances in generating, detecting and processing signals, known apex locating systems and practices remain imprecise. Some such imprecision is attributable to the mathematical limitations inherent to these techniques and associated algorithms. The equations employed by conventional apex finding techniques merely approximate the relationship between the electrode distance and the measured resistance or impedance. While some such algorithms achieve some degree of sophistication, they fail to account for subtle tissue characteristics and environmental variability. Thus, prior art systems remain handicapped in determining apical distance in the variety of conditions that exist. Consequently, known systems exhibit some level of imprecision and the above discussed risk of over/under root penetration and filling.
Environmental factors affecting a measurement process can further frustrate conventional root canal measuring devices. For instance, resistance measurements are often artificially decreased and otherwise corrupted in the presence of conductive medical liquids, water and blood in the root canal. Output of prior art systems may also be affected unfavorably by the respective sizes of the apical foramen and the measuring electrode, as well as apex morphology and abnormality. These environmental factors introduce an additional, nonlinear variable that can elude conventional algorithms. Thus, the calculated output of the prior art apex locating systems may be compromised and prone to error, often accompanied with the above discussed unfortunate results.
Developing and executing the algorithms of prior art systems can further require large amounts of processing and manpower, as well as other programming resources, to develop and improve upon equations that nonetheless remain fundamentally flawed. Consequently, and for in part the above delineated reasons, there exists a need for an improved manner of determining the depth of a root canal.